Semiconductor devices have been made larger and highly integrated. Fine processing techniques support such progress. Among these techniques, a lithography technique has been advanced by a reduction in the wavelength of a projection exposure apparatus and an increase in NA of a projection lens. However, this technique also reaches the limit, and a half pitch of approximately 40 nm is the limit in a method using ultraviolet rays or far ultraviolet rays. As a method for solving the limit, a method using EUV rays has been developed. However, this method has not yet been to practical use. On the other hand, a pattern forming method making full use of various processing techniques and a new method using characteristics of a material have been developed.
One of the methods is a self aligned double patterning (SADP) method of doubling a pattern by self-alignment (NPL 1) or a self aligned quadruple patterning (SAQP) method of quadrupling a pattern. In this method, a material having a high etching tolerance is selectively left on the side wall of a pattern formed by lithography, the pattern formed by lithography is deleted, and the remaining side wall is used as a pattern. Therefore, one pattern can be doubled. When this step is repeated twice, the pattern can also be quadrupled. In other words, the pitch of the pattern can be reduced to ½ or ¼.
As a method of multiplying a pattern n times by using characteristics of a material, a method using a self-induced organizing process and directed self assembly (DSA) (NPL 2) is known. In this method, self-organizing is performed using a material obtained by synthesizing two types of polymers called polymeric block copolymers and performing block coupling thereon, and using a difference in thermodynamic characteristics between the two types of polymers. It is possible to form a plurality of patterns on the inner side of a pattern (guide pattern) formed by lithography and to form a fine hole on the inner side of a large-sized hole in a self-aligned manner.
On the other hand, PTL 1 discloses that a plurality of reference lines are superimposed on a contour image obtained by a scanning electron microscope image of a photomask, and measurement is performed using the reference lines.